Hypertrophic cardiomyopathy (HCM) is a disease characterized by abnormal thickening of the ventricular myocardium and is inherited in an autosomal dominant fashion with variable expressivity. With recent advances in genetic techniques, there have been major advancements in understanding the genetic basis of HCM. Mutations of various sarcomeric proteins have been implicated, among which is ?- tropomyosin (TPM1), a protein that binds troponins and actin in thin filaments and plays a central role in the calcium dependent regulation of cardiac contraction. The underlying pathogenic mechanism of HCM caused by TPM1 mutations remains largely unknown due to 1) the inability to isolate/culture mutant cardiomyocytes for in vitro testing, and 2) the inaccessibility of human cardiomyocytes from patients with this disease. Recent advances in the generation of cardiomyocytes (iPSC-CMs) from induced pluripotent stem cells (iPSCs) present a novel opportunity to model myocardial diseases like HCM in vitro. This proposal is to study the role of TPM1 mutations in the pathogenesis of HCM by using disease- specific, human iPSC-CMs. For this, I have recruited two families with distinct TPM1 mutations with highly penetrant HCM phenotypes. Aim 1 is to determine the extent to which iPSC-CMs with the TPM1 mutations generated from these families can recapitulate HCM disease phenotypes. Aim 2 is to elucidate the mechanisms by which TPM1 mutations lead to pathologic hypertrophy by evaluating their molecular interactions as well as calcium binding kinetics in relation to HCM pathways. In summary, this proposed study will improve our understanding of the pathogenesis of HCM in TPM1 mutants, which may open doors for developing molecularly targeted, novel therapies.